
Aaron Loup is quickly becoming one of my favorite Mets, and it’s not just because of his affinity for a post-outing Busch Light. Loup is putting together an absolutely dominant season. He has pitched to the tune of a 1.45 ERA in 31 innings this year, a full run below his career-best 2.52 ERA that came last year with the Rays.
Aaron isn’t your prototypical modern reliever. He doesn’t throw (that) hard. He doesn’t throw 4-seam fastballs up in the zone. Yet, among relief pitchers with 30 or more appearances this year, Loup’s 1.66 FIP ranks fourth in baseball behind Craig Kimbrel, Ryan Pressly, and Josh Hader (his xFIP of 2.46 ranks 8th).
So, how is a side-arming, left-handed sinkerballer placing himself amongst the most elite closers in the game?
Tunneling His Fastballs
Loup hasn’t changed his repertoire since 2017 when he added a cutter to his arsenal. Since then, he has progressively began throwing his cutter more often in lieu of his sinker. This year, he’s throwing his cutter more often (37.1%), and his sinker less often (46.0%), than he ever has in his career.
His sinker is elite! Aaron gets 19.5 inches of horizontal movement and 27.9 inches of vertical movement, both well above MLB average. The cutter on the other hand keeps hitters honest; he gets 36.7 inches of drop, but averages just 1 inch of horizontal movement on this pitch. It isn’t so much the movement of his pitches that makes him great, rather it’s his release points.

These two pitches are coming out of the exact same tunnel with similar velocity; you can imagine how difficult it is for hitters to differentiate the sinker from the cutter. Even if a hitter picks up the pitch out of his hand, the sinker has 20 inches of horizontal movement and the cutter has almost none…good luck squaring that up. This is evident in Loup’s successes this year — hitters simply aren’t hitting the ball hard against him. He’s in the 98th percentile in MLB for barrel rate. Only 2 of his 78 batted balls allowed have been definitionally barreled up by hitters.
Location, Location, Location
Aaron’s location has also been impeccable, making it even tougher on hitters. He lives down in the zone and likes to work to his glove side (inside corner to a RH hitter). This zone chart from baseball savant shows just how often he hits his spots (and how rarely he misses).

His pinpoint accuracy has led to a career high 32.1% CSW%, and despite not throwing terribly hard Loup is striking out 29.8% of hitters while walking only 5.6% of them. Hitters are chasing more often than ever against him, and they are only making contact a little over half of the time they chase. Loup is simply befuddling hitters this year and the numbers show it.
What comes next for Aaron?
I don’t think anyone foresaw this dominant a season from Loup. His expected numbers, however, indicate he can continue mowing down opposing hitters with similar success; he ranks in the 88th percentile or above in xERA, xSLG, and xwOBA. Loup hasn’t had the chance to close games for the Mets this season, but with Edwin Díaz struggling, Loup could find himself in more high-leverage situations in the near future. Whether or not he gets an opportunity to close, I’m certain Aaron has a few more job-well-done Busch Lights on the horizon.
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All stats through July 21 @ 11am EST.